class AutomateIt::Plugin::Manager

Plugin::Manager

A manager provides high-level wrappers for features, e.g. installing software packages. It does not actually implement these features, but instead manages a set of drivers. When one of the manager’s wrapper methods is called, it queries the drivers to find the most suitable one and dispatches the user’s request to that driver.

For example, the PlatformManager is a Manager class that manages a set of Driver instances, including PlatformManager::Uname and PlatformManager::LSB. When you invoke the high-level PlatformManager#query wrapper method, it interrogates the drivers to find which one is best-suited for this method and then dispatches the request to that driver’s low-level implementation of this method.

The manager subclasses typically have no functionality of their own and just contain wrapper methods and documentation.

Attributes

drivers[RW]

Drivers for this manager as a hash of driver tokens to driver instances.

Public Class Methods

abstract_manager() click to toggle source

Declare that this manager class is abstract. It can be subclassed but will not be instantiated by the Interpreter.

# File lib/automateit/plugin/manager.rb, line 32
def self.abstract_manager
  classes.delete(self)
end
alias_methods(*methods) click to toggle source

Methods to alias into the Interpreter, specified as an array of symbols.

# File lib/automateit/plugin/manager.rb, line 40
def self.alias_methods(*methods)
  self.aliased_methods ||= Set.new
  self.aliased_methods.merge(methods.flatten)
end
driver_classes() click to toggle source

Driver classes used by this Manager.

# File lib/automateit/plugin/manager.rb, line 50
def self.driver_classes
  Driver.classes[token] || []
end

Public Instance Methods

[](token) click to toggle source

Returns the Driver with the specified token. E.g., :apt will return the APT driver.

# File lib/automateit/plugin/manager.rb, line 90
def [](token)
  return @drivers[token]
end
available?(method, *args, &block) click to toggle source

Is a driver available for this method and args? Uses automatic-detection routines and returns a boolean to indicate if a suitable driver is available. Unlike driver_for, this will not raise an exception.

# File lib/automateit/plugin/manager.rb, line 214
def available?(method, *args, &block)
  begin
    driver_for(method, *args, &block)
    true
  rescue NotImplementedError
    false
  end
end
default(token=nil) click to toggle source

Manipulate the default driver. Without arguments, gets the driver token as a symbol. With argument, sets the default driver to the token, e.g., the argument :apt will make the APT driver the default.

# File lib/automateit/plugin/manager.rb, line 97
def default(token=nil)
  if token.nil?
    @default
  else
    @default = token
  end
end
default=(token) click to toggle source

Set the default driver to the token. See also default.

# File lib/automateit/plugin/manager.rb, line 106
def default=(token)
  default(token)
end
dispatch(*args, &block) click to toggle source

Dispatch a method by guessing its name. This is the recommended way to write wrappers for a Manager methods.

Example:

class MyManager < Plugin::Manager
  # Your RDoc here
  def my_method(*args)
    # Will guess that you want to +dispatch_to+ the +my_method+ by
    # introspecting the name of the wrapper method.
    dispatch(*args)
  end
  ...
end
# File lib/automateit/plugin/manager.rb, line 123
def dispatch(*args, &block)
  # Extract caller's method as symbol to save user from having to specify it
  method = caller[0].match(/:in `(.+?)'/)[1].to_sym
  dispatch_to(method, *args, &block)
end
dispatch_safely(*args, &block) click to toggle source

Same as dispatch but returns nil if couldn’t dispatch, rather than raising an exception.

# File lib/automateit/plugin/manager.rb, line 171
def dispatch_safely(*args, &block)
  method = caller[0].match(/:in `(.+?)'/)[1].to_sym
  dispatch_safely_to(method, *args, &block)
end
dispatch_safely_to(method, *args, &block) click to toggle source

Same as dispatch_to but returns nil if couldn’t dispatch, rather than raising an exception.

# File lib/automateit/plugin/manager.rb, line 161
def dispatch_safely_to(method, *args, &block)
  begin
    dispatch_to(method, *args, &block)
  rescue NotImplementedError
    nil
  end
end
dispatch_to(method, *args, &block) click to toggle source

Dispatch the method with args and block to the appropriate driver. If the arguments include an option of the form :with => :mytoken argument, then the method will be dispatched to the driver represented by :mytoken. If no :with argument is specified, the most-suitable driver will be automatically selected. If no suitable driver is available, a NotImplementedError will be raised.

Examples:

# Run 'hostnames' method on most appropriate AddressManager driver:
address_manager.dispatch_to(:hostnames)

# Run AddressManager::Portable#hostnames
address_manager.dispatch_to(:hostnames, :with => :portable)

You will typically not want to use this method directly and instead write wrappers that call dispatch because it can guess the name of the method argument for you.

# File lib/automateit/plugin/manager.rb, line 146
def dispatch_to(method, *args, &block)
  list, options = args_and_opts(*args)
  driver = \
    if options and options[:with]
      @drivers[options[:with].to_sym]
    elsif default
      @drivers[default.to_sym]
    else
      driver_for(method, *args, &block)
    end
  driver.send(method, *args, &block)
end
driver_for(method, *args, &block) click to toggle source

Get the most suitable driver for this method and args. Uses automatic-detection routines and returns the most suitable driver instance found, else raises a NotImplementedError if no suitable driver is found.

# File lib/automateit/plugin/manager.rb, line 201
def driver_for(method, *args, &block)
  driver, level = driver_suitability_levels_for(method, *args, &block).sort_by{|k,v| v}.last
  if driver and level > 0
    return @drivers[driver]
  else
    raise NotImplementedError.new("can't find driver for method '#{method}' with arguments: #{args.inspect}")
  end
end
driver_suitability_levels_for(method, *args, &block) click to toggle source

Returns structure which helps choose a suitable driver for the method and args. Result is a hash of driver tokens and their suitability levels.

For example, if we ask the AddressManager for suitability levels for the AddressManager#hostnames method, we might find that there are two drivers (:portable is the token for AddressManager::Portable) and that the :linux driver is most appropriate because it has the highest suitability level:

address_manager.driver_suitability_levels_for(:hostnames)
# => {:portable=>1, :linux=>2}
# File lib/automateit/plugin/manager.rb, line 188
def driver_suitability_levels_for(method, *args, &block)
  results = {}
  @drivers.each_pair do |name, driver|
    next unless driver.respond_to?(method)
    results[name] = driver.suitability(method, *args, &block)
  end
  return results
end
instantiate_drivers() click to toggle source

Instantiate drivers for this manager. This method is smart enough that it can be called multiple times and will only instantiate drivers it hasn’t instantiated yet. All drivers will share an instance of the Interpreter, thus providing common state storage.

# File lib/automateit/plugin/manager.rb, line 73
def instantiate_drivers
  @drivers ||= {}
  self.class.driver_classes.each do |driver_class|
    driver_token = driver_class.token
    unless @drivers[driver_token]
      @drivers[driver_token] = driver_class.allocate
    end
  end
  self.class.driver_classes.each do |driver_class|
    driver_token = driver_class.token
    @drivers[driver_token].setup(
      :interpreter => @interpreter, :manager => self)
  end
end
setup(opts={}) click to toggle source

Options:

  • :default – The token of the driver to set as the default.

Calls superclass method AutomateIt::Common#setup
# File lib/automateit/plugin/manager.rb, line 56
def setup(opts={})
  super(opts)

  @default ||= nil

  instantiate_drivers

  if driver = opts[:default] || opts[:driver]
    default(opts[:default]) if opts[:default]
    @drivers[driver].setup(opts)
  end
end